The KX with the current lenses will be just fine. Its a wonderful camera very capable of taking excellent pictures. However, I would practice with it, so you would be familiar with it, rather than "on the job training" and being disappointed with the results. I would think that you will possibly be taking pictures like popcorn. On digital cameras, you can easily take 200+ a day. How long is your trip anticipated to be? Here is the manual - scoot back to page 298 and you can get about 550 JPG images on a 4GB card.
http://www.pentax.jp/english/support/man-pdf/k-x.pdf
Personally, without a laptop, I would take at least 4 - 4GB cards. They are cheap, and you do not need the fastest cards around. Just remember as you fill them up to slide the little locking latch to "locked", so that you will NOT reuse the card - and loose pictures.
4gb sdhc cards - Google Product Search
External flash - The camera has a built in flash which is ok and would probably be sufficient. I have never used an external flash, so I am not the best one to answer.
A small tripod with the remote IR would give you the ability to have the picture(s) - "Me and my bike in front of ________________" and you fill in the blank. Here are some ideas, it does not really need to be large......
http://www.google.com/products?q=small+travel+tripod&oe=utf-8&rls=org.mozill...ed=0CCsQrQQwAw
Also, remember you can roll in to just about any drug store and pick up AA batteries, but try to get Energizer e2 AA Lithium Battery - 4 Pack. You need 4 at a time and these should be good for at least 500+ shots (well at least in my 4 year old K100D). They go for about $10 a package (take at least one backup set with you).
http://www.amazon.com/Energizer-Ultimate-L91BP-4-Lithium-Battery/dp/B00003IEME